/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.spark.rdd

import org.apache.spark.{Partition, Partitioner, TaskContext}

import scala.reflect.ClassTag

/**
  * An RDD that applies the provided function to every partition of the parent RDD.
  */
private[spark] class MapPartitionsRDD[U: ClassTag, T: ClassTag](
                                                                   var prev: RDD[T],
                                                                   f: (TaskContext, Int, Iterator[T]) => Iterator[U], // (TaskContext, partition index, iterator)
                                                                   preservesPartitioning: Boolean = false)
    extends RDD[U](prev) {

    override val partitioner: Option[Partitioner] = if (preservesPartitioning) firstParent[T].partitioner else None

    override def getPartitions: Array[Partition] = firstParent[T].partitions

    override def compute(split: Partition, context: TaskContext): Iterator[U] =
        f(context, split.index, firstParent[T].iterator(split, context))

    override def clearDependencies() {
        super.clearDependencies()
        prev = null
    }
}
